That's the first time I ever heard of a reservoir for transmission fluid. The only reservoir I'm aware of is the hydraulic oil reservoir, which is connected to an oil cooler in the "sandwich" of coolers. That hydraulic system feeds the fan motor, power steering, etc. I suggest phoning Spartan customer service directly, they are quite helpful. Also there are several Cummins/Spartan service centers
in CA. that are fully-trained in servicing your chassis. Quite often the brand specific shops are no higher cost than independent shops, but they have specific training.
The fan motor leak sounds doubtful, my 1999 Spartan chassis w/42K doesn't leak_yet.
IMO that chassis repair shop sounds suspect.
2000 Winnebago Ultimate Freedom USQ40JD,
ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA." My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy